In order to assess the variability of the analgetic receptor, the essential moieties postulated to be necessary for analgetic activity will be incorporated into cis and trans 4a-methyloctahydrophenanthrene systems. The use of the angularly methylated tricyclic ring system presents several advantages: 1) we are able to define the geometry of the synthetic materials unequivocally by proton magnetic resonance; 2) the trans compounds have an energetically restricted conformation; 3) and, importantly, the proposed compounds closely resemble prototype analgetics. The synthesis and biological evaluation of the proposed substances will give a previously unobtainable insight into the geometry of the analgetic receptor.